2000 Disco II Diagnostic error codes

[CaliDiscowner]

I need help with my 2000 Discovery II. The "Service Engine Soon" warning light came on, and I pulled the error codes off of the computer. I received the following two error codes (P1171 & P1174):

1. P1171 System too rich (bank 1) Additive injector adaptive fuelling - rich limit exceeded LH bank
2. P1174 System too rich (bank 2) Additive injector adaptive fuelling - rich limit exceeded RH bank

I need to know what the course of action is to correct the error conditions? Any help you can offer is greatly appreciated!

Thanks!

Jim

12/20/2007 Update - I cleared the CEL codes and have driven about 60 miles. The CEL has not come back on again, and the vehicle seems to be running fine. Is it possible the two codes are related to running 89 octane fuel vs 91 octane fuel? For the first time in a long time I put 89 octane fuel in it, while not immediate, that's when the two codes appeared. Is there any relationship between the two, or am I just grasping at straws?